Origin and Properties

Cetraria Islandica, or Iceland moss, is a small plant, from two to four inches high, growing in the northern regions of Asia, Europe, and America, and abundant in some parts of New England. The whole plant is used. it consists of a dry, stiff frond or leaf, much divided, irregular in shape, and in the original state fringed with hairs upon the edges, most of which, however, have been lost as it is found in the shops. The colour is a mixture of different hues, irregularly dispersed, grayish-white, brownish, and reddish; there is no odour; and the taste is bitter and mucilaginous. The moss imparts all its virtues to boiling water. The important constituents are a starch-like substance in large proportion, constituting about 45 per cent., and a bitter principle amounting to 3 per cent. There is, besides, a little gum and sugar. The starch-like substance is insoluble in cold water, but is extracted by boiling water, and gelatinizes on cooling. in these respects it resembles starch, as also in producing a blue colour with iodine; but, as it differs in some other points, it has been called lichenin. The bitter principle is named cetrarin. it may be separated by macerating the plant in a very feeble solution of carbonate of potassa, which leaves the nutritive and demulcent principle, to be afterwards extracted by boiling with water. Prepared in this way, the moss is used as food, in times of scarcity, by the poorer population of some northern regions.

Medical Effects and Uses

Iceland moss unites gentle tonic with its nutritive and demulcent properties, and has consequently been employed in cases offering indications for these two effects, as in chronic pectoral affections with hectic symptoms, chronic dysentery and diarrhoea, and dyspepsia. Much was at one time hoped for, in phthisis, from a diet consisting mainly of a decoction of the moss; but experience has falsified all such expectations. it may be advantageously employed with a view to its tonic, nutritive, and demulcent effects; but this is all. it has been proposed to deprive it of its bitter principle, and then prepare it by decoction; but it thus loses the tonic property, and becomes a simple demulcent article of diet, in no respect superior to most of the class, and inferior to many. it is used almost exclusively in decoction.

The officinal Decoction (Decoctum Cetrariae, U. S., Br.) is made by boiling half a troyounce of the moss in a pint of water for fifteen minutes, straining with compression, and then adding, through the strainer, sufficient water to make the decoction measure a pint. The whole may be taken, in separate doses, in the period of twenty-four hours.